TREHALOSE AND SUCROSE PROTECT BOTH MEMBRANES AND PROTEINS IN INTACT BACTERIA DURING DRYING

The microorganisms Escherichia coli DH5 alpha and Bacillus thuringiens is I-ID-I show an increased tolerance to freeze-drying when dried in t he presence of the disaccharides trehalose and sucrose. When the bacte ria were dried with 100 mM trehalose, 70% of the E. coli and 57% of th e B. thuringiensis organisms survived, compared with 56 and 44%, respe ctively, when they were dried with sucrose. Only 8% of the E. coli and 14% of the B. thuringiensis organisms survived drying without the sug ars, Fourier transform infrared spectroscopy was used to investigate t he role of membrane phase transitions in the survival of the organisms during drying and rehydration. Both E. coli and B. thuringiensis show ed an increase of 30 to 40 degrees C in the temperature of their phosp holipid phase transition when dried without the sugars, while phase tr ansition temperatures of those dried with the sugars remained near tho se of the hydrated cells. A Fourier transform infrared spectroscopy mi croscope made it possible to investigate the effects of drying on the protein structure in the intact cells. The amide II peak shifts from 1 ,543 cm(-1) in the hydrated cells to about 1,533 cm(-1) in the cells d ried without sugar, There is no shift in the amide II peak when the ce lls are dried with trehalose or sucrose. We attribute the increased su rvival to the sugars' ability to lower the membrane phase transition t emperature and to protect protein structure in the dry state. In addit ion to increasing the immediate survival of both species, the addition of trehalose protected the cells from the adverse effects of exposure to light and air while dry, E. coli dried with trehalose and exposed to light and air for 4 h had an increase in CFU of between 2,000 and 4 ,000 times the number obtained with E. coli dried without trehalose, B . thuringiensis showed an increase in CFU of 150% in samples dried wit h trehalose compared with samples dried without trehalose. The cells d ried with sucrose did not show an increased tolerance to exposure foll owing drying.